From violent collision contests to celebrity-backed offshoots, spin-off sports are finding captive audiences. Their spectacle masks something more sinisterA few weeks ago a clip went viral of a strange new contact sport emerging from the antipodes. Two burly men, one of them holding a football, sprint at each other on a kind of catwalk, waiting for the bloop-bloop-bloop of an electronic countdown before they launch into their runs. Neither wears any kind of padding or protective gear. Surrounded by baying spectators, the men collide in the middle of the track, making impact through shoulders, knees, hips, stomachs: in most instances, one of the runners is knocked flat on his back or face from the force of the collision, and the other stands tall in triumph. “We are literally getting dumber as a civilization,” noted one of the many comments on the clip on X.Run Nation Championship, as this new sport is known, launched in Australia last year, and is now holding combines ahead of RNC03, i...